Casting Time 8 hours (2 phases of 4 hours)
Components V, S, M (gate spell connecting to the nameless gulf between dimensions, which has no effect other than allowing the ritual), F (a complete edition of the Necronomicon), L (in a fallen or desecrated temple of any deity at an elevated location, such as on a high hill or mountaintop), T (begin at sunset)
Optional Components SC (up to 10, each of whom must be an outer abomination, outer mutant, or outer spawn chanting from text; +1 bonus on ritual skill checks per 2)
Skill Checks Knowledge (planes) or Profession (Yog-Sothothery philosopher) DC 45, 2 successes
Range close (25 ft. + 5 ft./2 levels)
influence of Yog-Sothoth
Saving Throw none; Spell Resistance no
The ritual summons Yog-Sothoth through the gate into the caster’s plane, where its influence manifests centered on the gate. Yog-Sothoth can then allow through whatever other creatures or other Elder Beings from beyond that it desires.
The primary caster must be an outer spawn of Yog-Sothoth. During the ritual, when the first skill check succeeds, a 30-foot diameter circle of eldritch fire appears encircling the gate. This fire deals 4d6 points of fire damage to any creature that begins its turn in it or passes through it. At the completion of the ritual, Yog-Sothoth appears amid the flames.
Sandy Petersen’s Cthulhu Mythos, © 2017, Petersen Games; Authors: Sandy Petersen, Arthur Petersen, Ian Starcher.